The present invention relates to a device for ventilating a vehicle seat. Furthermore, the present invention relates to a vehicle seat which has such a ventilation device of the type in question.
Seat ventilation devices are known in general from the prior art; while, for example in the field of higher value motor vehicles, known devices of the type in question for supplying air to users who are in contact with a seat and/or back contact surface in the operating state of a vehicle seat and are acted upon with air sucked up by the fan unit—customarily from the vehicle interior—and discharged through the seat and/or back contact surface increasingly prevail, the comfort- and safety-increasing use, for example, of a seat ventilation device of the described type has long been tried and tested in aircraft, in construction vehicles, agricultural vehicles or military vehicles, especially in particularly stressful operating environments.
Traditionally, for the purpose of supplying air to the seat and/or back contact surface, a cushion manufactured customarily from an elastic foam material suitable for the sitting purposes of the user is provided with a through duct as air flow duct in such a manner that the fan unit, which is customarily accommodated in a modular manner in a fan housing, sucks up the additional air through said duct and then discharges same on the outlet side to the seat and/or back contact surface, wherein said outlet is frequently provided with an air-permeable, rigid cover unit in a manner known from the prior art. Said cover unit primarily has the purpose of preventing an unintentional sinking in of a user in the event of a punctiform weight loading of the cushion—what is referred to as the “knee test”, wherein, for this purpose, the cover unit, which is typically configured in the manner of a lattice, brings about a furthermore flat and fixed covering of the fan outlet at the end of the user-side end of the air flow duct.
In the case of devices presumed to be known from the prior art, said cover unit is typically designed as a termination or end-side delimitation of the fan housing, wherein, in particular from large scale manufacturing aspects and in order to realize the described modular concept, said assemblies can then be integrated, frequently also integrally, by suitable plastics injection molding technologies in order thereby to permit cost-effective manufacturability with easy installation properties, namely by simple insertion into the flow duct in the cushion.
A layer (which is flat and narrow relative to the cushion) of an air-permeable material which therefore conducts air along or parallel to the seat and/or back contact surface is frequently then also applied to the seat and/or back contact surface of the (foam) cushion, with the purpose of ensuring, for a top layer then stretched thereon (for example a seat leather layer suitably perforated for the air discharge), an air discharge which is distributed as far as possible over an area and is adapted to the anatomical user proportions of the seated user.
While specifically in the case of stressful environmental temperatures seat ventilation technologies of this type in the vehicle can significantly increase the user's travelling comfort and therefore passive operational safety of the vehicle equipped in this manner, the technology presumed to be known from the preamble and the generic type has nevertheless proven in need of improvement, in particular in respect of the special ventilation and installation conditions of a vehicle seat: an axial fan, which is customarily used within the scope of the fan unit forming the generic type, as the fan motor is dimensioned together with the further components of the air flow chain in such a manner that a delivery volume within the range of between approximately 4 liters/sec and approx. 10 liters/sec can be achieved, wherein typical seat contact surfaces of motor vehicles have a plurality of air flow ducts (spaced apart from one another and separated in terms of flow) together with respective fan units and cover units. As regards the dimensioning of the fan, including a diameter which can be realized for the fan rotor, the radial construction space is first of all restricted, for example by the problem described at the beginning that inhomogeneities in the (foam) cushion have a disadvantageous effect on the supporting properties of the cushion and the seat comfort, wherein even, for example, too large a diameter of the described cover unit could be potentially comfort-inhibiting (since it is itself rigid). Added to this is the problem that the plurality of mutually adjacent air flow ducts customarily to be provided in the same cushion have to have a sufficient minimum distance from one another in order to ensure a stable holding or anchoring of the fan units on or in the cushion.
In order, in view of these geometrical limits of the installation conditions in the vehicle seat and resultingly limited (radial) fan diameter, nevertheless to ensure a high air transport volume, it is customary to realize fan units, which are used for the seat ventilation, with high rotational speeds of the fan rotor; said fan units can reach up to 10 000 min−1.
However, it has then proved disadvantageous within the scope of the invention that, during the operation of a fan rotor with such high revolution speeds, vibrations occur which can be transmitted to the user via the rigid cover unit and can significantly impair the seat comfort. It has namely turned out that rotational speeds within the range mentioned may cause a vibration excitation of the system consisting of cover unit and fan housing, with the disadvantageous effect that specifically excited resonant frequencies may lead here to considerable vibration effects and to the described losses of comfort. Added to this is the potentially annoying generation of noise and the potential risk of mechanical impairments of the fan motor, which drives the fan rotor, together with bearings in such resonant situations.